The Short Answer
$10,000 compounded monthly at 5% becomes $16,470.09 after 10 years — $6,470.09 of it interest. The same $10,000 at the same 5% compounded annually would reach only $16,288.95, so switching from annual to monthly compounding is worth $181.15 over that decade.
Put another way: monthly compounding turns a stated 5.00% rate into an effective 5.12% APY. That is the entire benefit of compounding twelve times a year instead of once — real, but far smaller than most people assume. The rate you earn and the years you stay invested matter much more than the compounding schedule.
The formula behind all of it is A = P(1 + r/12)12t. Find your own numbers in the tables below:
- $10,000 by rate and term — the main lookup grid, 1% to 10%
- By starting amount — $1,000 through $100,000
- Monthly vs annual, side by side — what the frequency is actually worth
- With monthly contributions — $100 to $1,000 a month
How these figures were produced
Every balance on this page was computed with the same engine that powers our compound interest calculator, so any figure here reproduces exactly if you enter the same inputs there. Balances assume a fixed rate, no taxes, and no fees. Contribution figures assume deposits at the end of each month. Rounded to the nearest dollar unless cents are shown.
$10,000 Compounded Monthly: Balance by Rate and Term
This is the core lookup. Find your rate down the left, your time horizon across the top. All figures are for a single $10,000 deposit with no further contributions, compounded monthly.
| Annual Rate | 1 Year | 5 Years | 10 Years | 20 Years | 30 Years |
|---|---|---|---|---|---|
| 1% | $10,100 | $10,512 | $11,051 | $12,213 | $13,497 |
| 2% | $10,202 | $11,051 | $12,212 | $14,913 | $18,212 |
| 3% | $10,304 | $11,616 | $13,494 | $18,208 | $24,568 |
| 4% | $10,407 | $12,210 | $14,908 | $22,226 | $33,135 |
| 5% | $10,512 | $12,834 | $16,470 | $27,126 | $44,677 |
| 6% | $10,617 | $13,489 | $18,194 | $33,102 | $60,226 |
| 7% | $10,723 | $14,176 | $20,097 | $40,387 | $81,165 |
| 8% | $10,830 | $14,898 | $22,196 | $49,268 | $109,357 |
| 9% | $10,938 | $15,657 | $24,514 | $60,092 | $147,306 |
| 10% | $11,047 | $16,453 | $27,070 | $73,281 | $198,374 |
Two things worth noticing. First, the rate matters enormously over long horizons: at 30 years, 10% produces $198,374 while 5% produces $44,677 — not twice as much, but almost four and a half times as much. Second, the first year is nearly linear. At 5%, one year of monthly compounding earns $512 rather than the $500 simple interest would pay. Compounding needs time before it separates from plain arithmetic.
Your balance scales proportionally, so you can read this table for any starting amount: at 7% over 20 years, $10,000 becomes $40,387, which means $5,000 becomes half that ($20,194) and $50,000 becomes five times it ($201,937).
Balance by Starting Amount at 4.00%
The table above uses round rates for easy lookup. This one uses 4.00%, a rate you can actually get today: top high-yield savings accounts were paying roughly 3.75%–4.15% APY as of August 2026 (see where monthly compounding applies for sourced rates). Find your deposit down the left.
| You Deposit | 1 Year | 3 Years | 5 Years | 10 Years | 20 Years | Interest at 10 Yrs |
|---|---|---|---|---|---|---|
| $1,000 | $1,041 | $1,127 | $1,221 | $1,491 | $2,223 | $491 |
| $2,500 | $2,602 | $2,818 | $3,052 | $3,727 | $5,556 | $1,227 |
| $5,000 | $5,204 | $5,636 | $6,105 | $7,454 | $11,113 | $2,454 |
| $10,000 | $10,407 | $11,273 | $12,210 | $14,908 | $22,226 | $4,908 |
| $25,000 | $26,019 | $28,182 | $30,525 | $37,271 | $55,565 | $12,271 |
| $50,000 | $52,037 | $56,364 | $61,050 | $74,542 | $111,129 | $24,542 |
| $100,000 | $104,074 | $112,727 | $122,100 | $149,083 | $222,258 | $49,083 |
At 4.00% compounded monthly, a balance grows by roughly 49% over 10 years and roughly 122% over 20 years, whatever the starting amount. A $25,000 emergency fund parked at that rate earns $12,271 over a decade — if the rate holds, which no savings rate does. Savings rates are variable and follow the Federal Reserve; treat long-horizon rows here as illustrations of the math, not forecasts.
A 20-year savings-rate projection is not a forecast
High-yield savings and money market rates are variable and can change at any time, including to zero-point-something. The 20-year column shows what the arithmetic does if a rate holds, which is useful for comparing options — not a claim that any bank will pay 4.00% for twenty years. For long horizons, a diversified investment projection is the more realistic frame.
Monthly vs Annual Compounding: What the Frequency Is Actually Worth
This is the question the phrase "compounded monthly" is really asking, and the honest answer is that the difference is small at ordinary rates and short horizons, and only becomes interesting at high rates over decades. Both columns below use the same $10,000 and the same stated annual rate. The only thing that changes is how often interest is credited.
| Annual Rate | Monthly, 10 Yrs | Annual, 10 Yrs | Difference at 10 Yrs | Difference at 30 Yrs |
|---|---|---|---|---|
| 1% | $11,051 | $11,046 | $5 | $18 |
| 2% | $12,212 | $12,190 | $22 | $98 |
| 3% | $13,494 | $13,439 | $54 | $296 |
| 4% | $14,908 | $14,802 | $106 | $701 |
| 5% | $16,470 | $16,289 | $181 | $1,458 |
| 6% | $18,194 | $17,908 | $285 | $2,791 |
| 7% | $20,097 | $19,672 | $425 | $5,042 |
| 8% | $22,196 | $21,589 | $607 | $8,731 |
| 9% | $24,514 | $23,674 | $840 | $14,629 |
| 10% | $27,070 | $25,937 | $1,133 | $23,880 |
Read the last two columns together. At 3% over 10 years the frequency is worth $54 — on a $10,000 balance, that is a rounding error against the effect of finding a rate half a point higher. At 10% over 30 years it is worth $23,880, because the gap compounds on itself just like the interest does.
The practical rule: chase the APY, not the compounding schedule. A 4.10% account compounded annually beats a 4.00% account compounded daily, every time. APY already folds the compounding frequency in, which is exactly why banks are required to disclose it — see the APY conversion table.
Why the difference is capped
Compounding more often has a ceiling. At 5%, going from annual to monthly adds $181 over 10 years, but going from monthly all the way to continuous compounding adds only about $17 more. Daily compounding captures almost all of the available benefit, and monthly captures most of it. There is no compounding schedule that turns a mediocre rate into a good one.
Monthly Compounding With Monthly Contributions
Most people are not parking a lump sum — they are adding money every month. When contributions and compounding are both monthly, the balance is the sum of two pieces: the growth of whatever you started with, plus an annuity term for the deposits.
Formula with monthly contributions
FV = P(1 + r/12)12t + PMT × [((1 + r/12)12t − 1) ÷ (r/12)]
The first term grows your starting balance P. The second grows each monthly deposit PMT for however long it has left to compound.
The table below isolates the contributions: it assumes no starting balance, a 5% annual rate, monthly compounding, and deposits made at the end of each month.
| You Contribute | 5 Years | 10 Years | 20 Years | 30 Years | You Put In (30 Yrs) | Interest (30 Yrs) |
|---|---|---|---|---|---|---|
| $100/mo | $6,801 | $15,528 | $41,103 | $83,226 | $36,000 | $47,226 |
| $250/mo | $17,002 | $38,821 | $102,758 | $208,065 | $90,000 | $118,065 |
| $500/mo | $34,003 | $77,641 | $205,517 | $416,129 | $180,000 | $236,129 |
| $1,000/mo | $68,006 | $155,282 | $411,034 | $832,259 | $360,000 | $472,259 |
At every contribution level, the 30-year split is the same story: interest eventually exceeds everything you put in. Contributing $500 a month for 30 years means depositing $180,000 and finishing with $416,129 — $236,129 of it interest, which is about 57% of the final balance. The crossover — the month accumulated interest first exceeds everything deposited — happens in year 26 at a 5% rate, a little past the 25-year mark.
Because the annuity term is linear in the contribution, the rows scale cleanly: $250/month is exactly 2.5× the $100/month row, and $1,000/month is exactly 10× it. Halve your contribution and you halve the result.
Project a contribution schedule with your own rate and horizon →
Stated Rate vs Effective APY Under Monthly Compounding
A "5% rate compounded monthly" does not earn 5% a year — it earns 5.116%, because the interest credited in January itself earns interest for the remaining eleven months. That effective figure is the APY (annual percentage yield), and U.S. banks are required to disclose it precisely so that accounts with different compounding schedules can be compared on one number.
APY formula
APY = (1 + r/n)n − 1 — for monthly compounding, n = 12.
| Stated Rate | APY Quarterly | APY Monthly | APY Daily | Monthly Adds |
|---|---|---|---|---|
| 1.00% | 1.004% | 1.005% | 1.005% | +0.005 pts |
| 2.00% | 2.015% | 2.018% | 2.020% | +0.018 pts |
| 3.00% | 3.034% | 3.042% | 3.045% | +0.042 pts |
| 4.00% | 4.060% | 4.074% | 4.081% | +0.074 pts |
| 5.00% | 5.095% | 5.116% | 5.127% | +0.116 pts |
| 6.00% | 6.136% | 6.168% | 6.183% | +0.168 pts |
| 7.00% | 7.186% | 7.229% | 7.250% | +0.229 pts |
| 8.00% | 8.243% | 8.300% | 8.328% | +0.300 pts |
| 9.00% | 9.308% | 9.381% | 9.416% | +0.381 pts |
| 10.00% | 10.381% | 10.471% | 10.516% | +0.471 pts |
The gap between a stated rate and its monthly APY is under a tenth of a point below 5%. This is why comparing a bank's advertised APY against another bank's advertised APY is enough — you do not need to know either one's compounding schedule. For how a stated rate differs from APR on the borrowing side, see our guide to APR vs interest rate.
Where You Actually Earn Monthly Compound Interest
Most deposit accounts compound daily or monthly, and the difference between those two is trivial (see Section 4). What is not trivial is the rate. The table below separates top-of-market offers from national averages, because they are far apart right now and quoting only the headline rate would be misleading.
| Account Type | Top Offers (Aug 2026) | Compounding | Best For |
|---|---|---|---|
| High-Yield Savings | 3.75%–4.15% APY | Daily or monthly | Emergency funds, short-term goals |
| Money Market Accounts | 3.50%–4.00% APY | Daily or monthly | Larger balances needing check-writing |
| Certificates of Deposit | 3.80%–4.50% APY | Daily, monthly, or quarterly | Money with a known timeline |
| Traditional Savings | 0.38% national avg | Monthly | Little reason to hold a balance here |
| Series I Savings Bonds | 4.26% composite | Semiannual | Inflation protection, 1-year lockup |
| Index Funds (401k / IRA) | No fixed rate | Not a schedule — see below | Long-term retirement growth |
Sourcing and dates for the table above. The high-yield savings, money market, and CD rows are top widely available offers, not national averages, re-verified against Bankrate's rate surveys on August 13, 2026. Those bands are stated once, in the table — every top-of-band figure elsewhere on this page refers back to it. The contrast with averages is stark: the FDIC national average across all savings accounts was 0.38% as of July 20, 2026; Bankrate put the national average 1-year CD at 2.03% as of August 12, 2026, roughly half the top 1-year offers; and Bankrate's average money market APY across all tracked accounts was 0.45% as of August 13, 2026, against the 4.00% top offer in the table above. Shopping matters more than compounding frequency.
The Series I bond figure is the 4.26% composite rate that the U.S. Treasury announced on May 1, 2026 for bonds issued May 2026 through October 2026, combining a 0.90% fixed rate with the semiannual inflation component. It applies for the first six months after issue and then resets; I bonds compound semiannually, not monthly, and cannot be redeemed within the first 12 months.
The last row deserves care. Stock and bond funds do not pay a fixed rate on a compounding schedule — their value moves with markets, and the "compounding" is really the reinvestment of dividends plus price appreciation, which can be negative in any given year. Applying a smooth 7% monthly-compounding curve to a stock portfolio, as the tables on this page do, describes an average, not any actual year. Our investment growth guide shows how far individual years scatter around that average.
Rates change constantly
Deposit rates move with the Federal Reserve and with each bank's funding needs, sometimes weekly. The figures above were verified against Bankrate, NerdWallet, FDIC, and TreasuryDirect data in August 2026 and are already drifting. Confirm the current APY directly with the institution before you move money.
How Long Money Takes to Double, Compounded Monthly
The Rule of 72 — divide 72 by the rate — is the standard mental shortcut, and it is a good one. It is also consistently a little pessimistic when interest actually compounds monthly, because it does not account for the twelve creditings a year.
| Annual Rate | Rule of 72 Estimate | Actual (Monthly) | Rule Overstates By |
|---|---|---|---|
| 3% | 24.0 years | 23.1 years | 0.9 years |
| 4% | 18.0 years | 17.4 years | 0.6 years |
| 5% | 14.4 years | 13.9 years | 0.5 years |
| 6% | 12.0 years | 11.6 years | 0.4 years |
| 7% | 10.3 years | 9.9 years | 0.4 years |
| 8% | 9.0 years | 8.7 years | 0.3 years |
| 10% | 7.2 years | 7.0 years | 0.2 years |
| 12% | 6.0 years | 5.8 years | 0.2 years |
Doubling time is independent of the amount — $1,000 and $1,000,000 both double in 13.9 years at 5% compounded monthly. The exact expression is t = ln(2) ÷ (12 × ln(1 + r/12)), but the Rule of 72 is close enough for mental arithmetic and errs on the conservative side. For a fuller treatment of the rule and its limits, see our guide to how compound interest works.
Calculating Monthly Compound Interest in Excel or Google Sheets
Both applications use the same FV (future value) function, and both need the same two adjustments for monthly compounding: divide the rate by 12 and multiply the years by 12.
Lump sum, no contributions
=FV(rate/12, years*12, 0, -starting_balance)
$10,000 at 5% for 10 years: =FV(0.05/12, 10*12, 0, -10000) returns $16,470.09.
With monthly contributions
=FV(rate/12, years*12, -monthly_contribution, -starting_balance)
$500 a month at 5% for 30 years with no starting balance: =FV(0.05/12, 30*12, -500, 0) returns $416,129.
The minus signs are not optional. Excel follows a cash-flow convention where money you pay in is negative and money you receive is positive, so omitting them returns a negative future value. To get just the interest, subtract your total deposits: =FV(...) - (monthly_contribution * years * 12) - starting_balance.
Frequently Asked Questions
Use A = P(1 + r/12)12t. Divide the annual rate by 12 to get the monthly rate, multiply the number of years by 12 to get the number of months, then raise (1 + monthly rate) to that power and multiply by your starting balance. For $10,000 at 5% for 10 years: 0.05/12 = 0.00416667 monthly, 10 × 12 = 120 months, and 10000 × (1.00416667)120 = $16,470.09.
$10,000 at 5% compounded monthly grows to $10,512 after 1 year, $12,834 after 5 years, $16,470.09 after 10 years, $27,126 after 20 years, and $44,677 after 30 years. The 10-year figure represents $6,470.09 of interest on your original $10,000.
Less than most people expect. On $10,000 over 10 years, monthly compounding beats annual compounding by $181.15 at 5% ($16,470 versus $16,289) and by $425 at 7%. The gap widens with both the rate and the time horizon: over 30 years at 10% it reaches $23,880. At typical savings rates of 3–4% over a few years, the difference is a few dollars to a few hundred. Compounding frequency is real but minor compared with the rate itself and the time you stay invested.
5.116%. The effective annual yield of a stated 5% rate compounded monthly is (1 + 0.05/12)12 − 1 = 5.116%. That is what APY means: the stated rate after compounding is folded in. Monthly compounding adds about 0.116 percentage points at a 5% stated rate, 0.074 points at 4%, and 0.229 points at 7%. Always compare accounts on APY, because APY already accounts for the compounding schedule.
Add an annuity term to the formula: FV = PMT × [((1 + r/12)12t − 1) ÷ (r/12)], then add the growth of any starting balance. Contributing $500 a month at 5% compounded monthly, with no starting balance, produces $34,003 after 5 years, $77,641 after 10 years, $205,517 after 20 years, and $416,129 after 30 years. At 30 years you would have contributed $180,000, so $236,129 of that balance is interest.
Use the FV function with the rate divided by 12 and the term multiplied by 12: =FV(rate/12, years*12, -monthly_contribution, -starting_balance). For $10,000 at 5% for 10 years with no contributions, =FV(0.05/12, 10*12, 0, -10000) returns $16,470.09. Google Sheets uses the same FV function with identical syntax. The minus signs matter because Excel treats money you pay in as a negative cash flow.
At 5% compounded monthly, money doubles in 13.9 years; at 7% it takes 9.9 years, and at 10% it takes 7.0 years. The Rule of 72 shortcut (72 divided by the rate) slightly overstates the true doubling time under monthly compounding, by about 0.9 years at 3% and 0.2 years at 10%, because it does not account for compounding happening twelve times a year.
Sources
- SEC Investor.gov — Compound Interest Calculator (opens in new tab) (formula reference)
- TreasuryDirect — Savings Bond Rates announcement, May 1, 2026 (opens in new tab) (I bond 4.26% composite / 0.90% fixed, May–Oct 2026 issues)
- FDIC — National Rates and Rate Caps (opens in new tab) (0.38% national average savings, as of July 20, 2026)
- Bankrate — Best High-Yield Savings Account Rates (opens in new tab) (August 2026 top offers)
- Bankrate — Money Market Account Rates (opens in new tab) (August 2026 top offers and averages)
- Bankrate — CD Rates (opens in new tab) (August 2026 top offers; 1-year national average 2.03% as of August 12, 2026)
- NerdWallet — Best High-Yield Savings Accounts (opens in new tab) (August 2026 cross-check)
- Federal Reserve — Selected Interest Rates (H.15) (opens in new tab)
- FDIC — Deposit Insurance (opens in new tab)
Important Disclaimer
Disclaimer: This content is for educational and informational purposes only and does not constitute financial, tax, or legal advice. Individual circumstances vary, and you should consult with a qualified financial professional before making investment decisions. While we strive for accuracy, interest rates and financial products change frequently. Calculations assume a constant rate and do not account for taxes, fees, or market fluctuations unless specified. Deposit rates cited are current as of August 2026 and change without notice.
Content reviewed by Mark at Markco Labs. Learn more about our accuracy standards.